An external resonance type laser module including a quantum cascade laser and a diffraction grating for diffracting and reflecting light emitted from the quantum cascade laser has been known as a light source used for spectroscopic analysis and used to perform wavelength sweeping (scanning). In such an external resonance type laser module, for example, the diffraction grating is fixed on a rotation stage, and the rotation stage is rotated by an actuator to change a direction of the diffraction grating, whereby a wavelength of output light is variable (for example, see U.S. Pat. No. 7,903,704).
The external resonance type laser module described above is required to be able to realize highly accurate measurement when used for spectroscopic analysis while attempting miniaturization and improvement in reliability.